The Crusades: The Authoritative History of the War for the Holy Land, by Thomas Asbridge, is a broad overview of the major Crusades by Latin Christian states under the guidance (albeit loosely) of the Papal States. The ultimate goals of the Crusades ranged from taking back the holy city if Jerusalem from Muslim control, propping up subsequent Catholic states in the region, and other times targeted fellow Christian states (the Fourth Crusade - directed at the Roman Empire in Constantinople). The Crusades by no means had universal support, and were often used as excuses to extend temporal power, compete with rival monarchs and achieve prestigious military victories. These objectives often mixed with the religious notions of Crusade.
The First Crusade was a bit of a spontaneous construction, although planning for something of its kind - as well as a few expeditions by European counts had existed previously. The Roman Emperor Alexios Komnenos had requested aid in his war against the Seljuk Turks in Anatolia. In 1095, Pope Urban II answered the call, and preachers across Europe began asking for aid from devout Christian soldiers. The mustering quickly became overwhelming - thousands of lesser nobles and their retinues answered the call, and a large force was mustered and marched toward Constantinople. The Emperor Alexios was alarmed at the size of the force, most lesser nobles and company from the Frankish regions, but hoped to used their martial prowess to reconquer parts of Anatolia. Mistrust, however, did exist between Christian camps. A rivalry between Provencal forces from southern France, and Norman forces from Northern France/Sicily emerged. And the Byzantines did not trust any of the crusading forces.
The Crusaders agreed to return all conquered lands to Byzantium, and quickly overran the important fortress of Nicaea in Anatolia. The two rival armies then split, one marching East toward Edessa, and the other south toward Antioch. The Eastern army succeeded in defeating a Seljuk force and captured Edessa and surrounding lands, forming the County of Edessa as a Crusading state. Similarly, the Anotiochene army marched on the Antioch, and subjected it to a grueling siege, eventually successful. After this, the force marched on to Jerusalem, taking that city as well, and subjecting it to brutal slaughter. New Crusader states - the County of Tripoli, the Principality of Antioch, and the Kingdom of Jerusalem were formed.
The conquests were so successful because of disunity in the Islamic world. The temporal power of the Caliph in Baghdad had waned over the years leading up to the crusades, and the Levant was a region contested by rival forces in Aleppo, Damascus and Fatmid Egypt. This disunity negated a unified response by Arab rival powers, and indeed the Crusaders even managed to sign a treaty of friendship (albeit a brief one) with Fatmid Egypt. This disunity allowed the new fledgling crusader states - weak in temporal power, low on manpower and lacking control over the countryside of their new states - to consolidate control. The new states quickly sought to solidify control over the surrounding areas, as well as the Levantine coast. Cities such as Beirut, Jaffa, Acre and so on were captured and fortified. The Crusaders pushed inland as well, securing Palestine, the Jordan region and extended territories in modern Syria, Lebanon and Turkey. Relations between the Crusaders and Fatmid Egypt soured, however, after Egypt retained control of Ascalon, a key fortress on the Palestinian coast and the "Gateway" to Egypt as a staging point to cross the Sinai Desert.
Islamic forces began to grow closer together in the face of this new threat from Europe, although rivalries still existed. This gave rise to a new dynasty in the region. The Zangri's - Turkish warriors working under the Caliph of Baghdad, began to consolidate control in Syria. Zangri would eventually succeed in destroying the County of Edessa - sparking the Second Crusade - an unmitigated disaster where Christian forces divided into two, and stoically (and perhaps foolishly) marched to their deaths at the hands of Seljuk warriors in the interior of Turkey. Meanwhile, political squabbles between the states of the Levant allowed Zangri's successor - Nur ad-Din, to begin to chip away at the Crusading states. Much of Palestine was overrun, and the county of Tripoli severely reduced in size. The greatest threat to the Christian states, however, was the coming of Saladin - who invaded Fatmid Egypt for his lord Nur ad-Din, and then declared autonomy. Eventually, Saladin would succeed in taking both Damascus and Aleppo, and extending his control over Western Iraq as well. He would also succeed in briefly destroying the Crusading sates (except Antioch), occupying Jerusalem and starting the Third Crusade.
The Third Crusade may be the most famous after the First. Great monarchs like Philip of France and Richard Lionheart of England/Aquitaine would march on the East, joined by the might Frederick Barbarossa, Holy Roman Emperor in Germany. Richard and Philip were both reluctant, at first to join the Crusade. Both were temporarily united in reducing the power of Henry the I, Richards father and King of England. Richard succeeded in defeating his father, and eventually took over as King of England, controlling lands also in southern France. Philip was King of France and eventual rival of Richard, looking to take back control of French lands controlled by the English Monarchs. Both, however, out aside their rivalries in Europe to continue pursuing them in the Holy Lands. Richard and Philip took ships to the Levant, while Frederick of Germany marched across Anatolia. Richard stopped to support family members in dynastic squabbles in Sicily, and also defeated the Greek rulers of Cyprus, before landing in the Holy Lands to assist in the epic siege of Acre. Philip had been their earlier, building large modern siege weapons to try and reduce Acres walls. Saladin was camped nearby, constantly harassing Crusader forces and trying to relieve the siege with men and supplies. Frederick marched East, encountering resistance from the Byzantines and Seljuk Turks, but swiftly overcame these in siege warfare against the Greeks, and decisive skirmishing against the Turks. However, tragedy befell, as Frederick crossed a river, he slipped and fell from his horse, and drowned.
The Third Crusade ended up being a largely successful venture, especially for Richard. He subdued Cyprus and created a new Crusader state there. Philip left quickly after the fall of Acre, his quest fulfilled. But Richard stayed on, reconquering much of coastal Palestine and Lebanon for Jerusalem - although he fell short of taking the City itself. Saladin was largely on the back foot, and after his resounding success early on, he lost some territory to the Crusaders, and saw his dynasty shaken by competing factions. Asbridge continues by looking briefly at the Fourth Crusade, which never even reached the Levant - instead attacking Byzantine possessions in Greece and Hungarian forces in Zara (Croatia) at the behest of the Crusades Venetian financiers. The Fifth and Sixth Crusade did reach the Holy Land, and managed to briefly reconquer the Holy City for Jerusalem, before the Crusader states finally crumbled under concentrated Mamluk assault.
Asbridge has done an excellent job examining the Crusades. The States created in the Levant were largely Feudal in nature, and temporal in power, even though they were largely created by religious fervor from Europe. The States squabbled amongst themselves just as much as against there common enemies, and ultimately succumbed to concentrated and unified assault by a large Islamic power. They took advantage of weak and fractured Muslim rule, but were unable to create a lasting impression on the region, and were ultimately swallowed whole. After the crusading period - which lasted roughly from the 12th to 14th centuries, the tide of Crusaders faltered in the Levant, and these regions ultimately became provinces of large Muslim powers, first Ayubbid, then Mamluk and finally Ottoman, for centuries. Asbridge looks at factors affecting both Muslim powers in the region, and temporal Christian states that both built and became the Crusader states of Outremer. He also examines scant evidence of cross cultural exchanges and trading between these seeming enemies, and notes little changed for the subjects of the region beyond marauding armies.
Asbridge focuses heavily on the period between the First and Third Crusade, largely examining the composition of the Crusader states, as well as the growth of Saladin and others in the region as they sought to unify Islamic power in the face of Crusader assaults, and form a lasting and cohesive dynasty composing land from Egypt to Iraq - no easy feat at this time. The Fifth and Sixth Crusade are only briefly examined. All things told, this is a very interesting book with a comprehensive examination of the history of both the construction and destruction of Europe's Crusading states, and how these states affected the region. Easily recommended for fans of Medieval history, and those looking for a good and unbiased overview of the Crusading period.